Flash floods are the deadliest storm-related hazard in the US, causing more fatalities in an average year than tornadoes, hurricanes, or lightning. Over the last 10 years, the threat of flash flooding in the US has grown as severe rainfall events have become more frequent and intense. In 2025, extreme cloudburst rains in the Texas Hill Country caused the Guadalupe River to surge more than 25 feet overnight, leading to the deaths of more than 80 people. The destructive, fast-moving waters wiped out homes and vehicles and led to the disappearance of 27 girls who were attending a riverside summer camp in Kerr County. In 2024, Hurricane Helene claimed the lives of about 250 people, many of whom were victims of massive inland flooding across Florida, Georgia, Tennessee, Virginia, and the Carolinas. In 2022, catastrophic flooding in eastern Kentucky killed 45 people and destroyed thousands of homes and businesses overnight. According to the National Weather Service (NWS), the violent flooding was caused by training thunderstorms, a setup in which multiple thunderstorms repeatedly move over the same area. Twenty people were killed in the small middle-Tennessee town of Waverly in August 2021 after more than 17 inches of rain fell in less than 24 hours, causing local creeks to overflow. Among those killed in the Waverly flood were twin babies who were swept from their father’s arms as rushing water overwhelmed the family’s apartment complex. Hurricane Harvey hit Texas in August 2017. The powerful Category 4 storm dumped several feet of rain on many Gulf communities and the Houston area. According to the National Hurricane Center, Harvey killed at least 68 people, with all but three deaths being directly attributed to intense freshwater flooding.
